There's your problem. For men, 3% is the Essential Fat. I.E. the amount you to live. 5% is considered the lowest safe level of Body Fat for men. If you BF% was really 3%...you were putting yourself at risk. Also, you do not state that you are sure the gain was fat. You say you figure it was. Has this been tested ? What is your current BF% ? LBM as compared to before ? If your BF is still below 5%, you need to put on a little more fat. If your Body Fat is really 3% and you are trying to reduce it, you need professional help...as you likely have an eating disorder.